In the papermaking field, for example, various papermaking additives such as yield-improving agents and water filtering property-improving agents so as to improve the runnability and work efficiency by improving the yield and water filtering property of pulp and/or fillers which are/is a material, and papermaking additives so as to improve the strength of paper products have been conventionally known.
To be more specific, as such a papermaking additive, for example, an amphoteric polymer compound obtained by adding methyl diallylamine and carboxylic acid (fumaric acid) to water to be heated and dissolved to be then polymerized by adding a polymerization initiator thereto has been proposed, and the use of the amphoteric polymer compound, as a paper additive, has been also proposed (ref: Patent Document 1 (Synthetic Example 4)).